1. Field of the Invention
The present invention discloses new antimicrobial compositions to control plant diseases and to prevent microbial spoilage of crops.
2. Description of Related Art
It is estimated that about 25% of the world crop production is lost due to microbial spoilage, of which spoilage by fungi is by far the most important cause. Not only from an economical point of view, but also from a humane point of view it is of great importance to prevent spoilage of food products. After all, in many parts of the world people suffer from hunger.
Success in combating plant and crop diseases and in reducing the damage they cause to yields and quality depends greatly on the timely application of fungicides. The prolonged and frequent use of many fungicides such as e.g. benzamidazoles has contributed to reduce their effectiveness thanks to the development of phenomena of resistance.
An important group of fungicides are the triazoles. The first triazole that was introduced was triadimefon. This triazole was introduced in 1976 by Bayer (see Kuck et al., 1987). Triadimefon provided curative as well as protective activity, low application rates and excellent redistribution in the plant. Additional triazole fungicides were introduced over the next two decades with improved potency and plant safety (e.g., epoxiconazole), a broader effective spectrum (e.g., propiconazole, tebuconazole) or specialized applications (e.g., difenoconazole and triticonazole for seed treatment) (see Kuck et al., 1987). Next to their use in protecting agricultural products such as harvested fruit or vegetables from phytopathogenic fungi (see EP 2 036 438 A1) or cereals from mycotoxin contamination (see WO 2007/009969), triazoles have been used to protect food products from fungal decay (see EP 0 101 102 A2).
Triazole fungicides however have not been immune to challenges in their development and maintenance. They have well-documented side effects on plants. Application to shoots and roots often reduces elongation and causes leaves to be smaller, thicker, and greener. Treated plants may be delayed in senescence, which can impede harvest or improve yields, depending on the crop (see Buchenauer, 1987).
A larger concern has been resistance development, since triazole fungicides have many of the same properties as the benzimidazoles. Resistance to the triazole fungicides developed first in the powdery mildews and has also been observed on other diseases (see Kuck et al., 1987; Buchenauer, 1987; Ma et al., 2002).
Moreover, although the launch of triazole fungicides provided potent, systemic fungicide solutions for Ascomycete and Basidiomycete diseases, control of devastating Oomycete diseases such as potato late blight and grape downy mildew is limited and root rots of established plants (caused by Phytophthora and Pythium) and systemic downy mildews cannot be controlled at all by applying triazole fungicides.
For many decades, the polyene macrolide antimycotic natamycin has been used to prevent fungal growth on food products such as cheeses and sausages. For instance, in EP 0 748 588 A1 the use of fungal compositions comprising a polyene antifungal agent and an imidazole antifungal agent for the treatment of food and agricultural products is described. This natural preservative, which is produced by fermentation using Streptomyces natalensis, is widely used throughout the world as a food preservative and has a long history of safe use in the food industry. It is very effective against all known food spoilage fungi. Although natamycin has been applied for many years in e.g. the cheese industry, up to now development of resistant fungal species has never been observed.
Consequently, it can be concluded that there is a severe need for more effective antimicrobial compositions, e.g. antifungal compositions, for the treatment of fungal growth in and on plants and crops.